Digital fitness trackers such as the Fitbit from FitBit Inc. and the UP from Jawbone, two San Francisco-based startups, have attracted an avid set of CEO early adopters. With their constant stream of numbers gauging the wearer's physical activity and hours of sleep, the bracelet-like trackers help data-obsessed executives treat their wellness the way they would treat any business problem: Analyze it and fix it.

Three wearable health trackers are ready for your wrist right now: the Nike FuelBand, Jawbone Up and Fitbit Force. Digits puts them through their paces to see which may work best for you.

The devices, some of which use accelerometers, measure wearers' movements and in many cases the length and quality of their sleep. That data is transmitted to a website or smartphone app, where the user can view and share the stats. For many chiefs, these companion apps have become an under-the-radar social network, where they keep tabs on peers, stake out friendly rivalries or seek encouragement to nap more often.

Mr. Dell wears a FitBit, as does Mr. Benioff, allowing them to stay current on each other's latest data. When a recent bout of sickness caused the Salesforce leader to miss a few days of exercise, a worried Mr. Dell flagged the discrepancy on the FitBit network and gave his friend a call, recounted Mr. Benioff during a digital-trends discussion at the World Economic Forum in Davos in January.

"He's competing with me," joked Mr. Benioff, who has credited the FitBit with helping him lose 30 pounds and sports several other pieces of wearable tech.

The market for digital fitness devices, which is dominated by FitBit, Jawbone and
Nike Inc.
products, hit a high of $330 million in 2013, according to consumer researchers at NPD Group. FitBit has the largest market share of the three, though a recent recall of the FitBit Force, suspected of triggering rashes for some users, has threatened its outlook.

Caroline Ghosn,
the founder and CEO of the professional women's network Levo League, wears a black UP band on her right wrist. Having metrics handy has helped her prioritize well-being, says Ms. Ghosn, 27 years old. She now sleeps an average of 8.14 hours a night, according to recent Jawbone readings.

Ms. Ghosn kicked off her fitness quest with
Ruzwana Bashir,
the CEO of online-travel concierge Peek.com, at a San Francisco tea lounge in January 2013, confessing to her friend that she felt "too tired to enjoy the highs of success." The discussion led the women to agree to a "100-day plan," a period in which they would use their digital trackers to help each other set healthy habits regarding their exercise and sleep.

Each had to answer to the other when she failed to keep up. Once, Ms. Bashir took a red-eye flight to New York, and Ms. Ghosn noted her friend's lack of sleep. She summoned Ms. Bashir to her apartment to nap before that day's meetings. "It's a constant battle for us," Ms. Bashir says, but sharing the struggle with a peer has helped her see it is possible—and permissible—for a chief executive to put her own health first.

For Ms. Bashir, 30, who is a contributor to Style.com, health even came at the expense of fashion. The rubbery Jawbone is "not a beautiful item to be wearing every day," she says.

Showing how entwined the CEO fitness-tracker network has become, Ms. Bashir recalls a dinner last fall when she was seated with several successful chief executives and talk centered not on business but on sleep and wellness.

Mr. Chenault, who wears a Jawbone band, mentioned that he works out for up to 90 minutes a day and gets plenty of sleep, too.
René Lacerte,
the CEO of online-payments system Bill.com, and
Philip Rosedale,
the founder of "Second Life" maker Linden Lab and now a co-founder of High Fidelity, another virtual-game venture, both use the Nike+ Running app, which tracks pace, time and calories burned.

Mr. Rosedale, 45, particularly enjoys the Nike+ app's Leaderboard, which ranks a person's network according to total miles run that month. Recently he has been jockeying to pass
Danny Trinh,
a former product designer at the Path social network. "I'm honored that Philip is trying to keep up with me," says Mr. Trinh, 23, now in the midst of launching a new venture.

Mr. Lacerte, who became hooked on fitness after reading "Younger Next Year," an exercise almanac written by a former corporate lawyer, describes his wellness as a string of data points. He says he has lost about 30 pounds in the past 15 months, strives to work out about 320 days a year and log 100 miles a month on his Nike+ watch, and sleeps an average of seven hours a night.